The spectral phonon properties in defected graphene were unclear due to the lack of advanced techniques on predicting the phonon-defect scattering rate without fitting parameters. Taking advantages of the extended phonon normal mode analysis, we obtained the spectral phonon relaxation time and mean free path (MFP) in defected graphene and studied the impacts of three common types of defects, Stone-Thrower-Wales (STW) defect, double vacancy (DV), and mono vacancy (MV). Phonon-STW defect scattering rate is found to have no significant frequency dependence, and as a result, the relative contribution of long-wavelength phonons sharply decreases. In contrast, the phonon scattering by DVs or MVs exhibits a frequency dependence of τ −1 p−d ∼ ω 1.1−1.3 except a few long-wavelength phonons, providing a critical revisit to the traditionally used ∼ ω 4 dependence. We note that although MV-defected graphene has the lowest thermal conductivity as compared to the other two defected graphene samples at the same defect concentration, it has a portion of phonons with the longest MFP. The contribution from the long-MFP and longwavelength phonons does not decrease much as the vacancy concentration increases. STW defect and MV block more out-of-plane modes than in-plane modes while DV has less bias on which mode to block. As the MV concentration increases from 0 to 1.1%, the relative contribution from out-of-plane modes decreases from 30% to 18%, while that of the transverse acoustic mode remains at around 30%. These findings of spectral phonon properties can provide more insights than the effective properties, and benefit the prospective phononic engineering.

High-performance thermal management materials are essential in miniaturized, highly integrated, and high-power modern electronics for heat dissipation. In this context, the large interface thermal resistance (ITR) that occurs between fillers and the organic matrix in polymer-based nanocomposites greatly limits their thermal conductive performance. Herein, through-plane direction aligned three-dimensional (3D) MXene/silver (Ag) aerogels are designed as heat transferring skeletons for epoxy nanocomposites. Ag nanoparticles (NPs) were in situ decorated on exfoliated MXene nanosheets to ensure good contact, and subsequent welding of ice-templated MXene/Ag nanofillers at low temperature of ∼200 °C reduced contact resistance between individual MXene sheets. Monte Carlo simulations suggest that thermal interficial resistance (R 0) of the MXene/Ag–epoxy nanocomposite was 4.5 × 10–7 m2 W–1 K–1, which was less than that of the MXene–epoxy nanocomposite (R c = 5.2 × 10–7 m2 W–1 K–1). Furthermore, a large-scale atomic/molecular massively parallel simulator was employed to calculate the interfacial resistance. It was found that R MXene = 2.4 × 10–9 m2 K W–1, and R MXene‑Ag = 2.0 ×10–9 m2 K W–1, respectively, indicating that the Ag NP enhanced the interfacial heat transport. At a relatively low loading of 15.1 vol %, through-plane thermal conductivity reached a value as high as 2.65 W m–1 K–1, which is 1225 % higher than that of pure epoxy resin. Furthermore, MXene/Ag–epoxy nanocomposite film exhibits an impressive thermal conductive property when applied on a Millet 8 and Dell computer for heat dissipation.

Conventional polymer composites normally suffer from undesired thermal conductivity enhancement which has hampered the development of modern electronics as they face a stricter heat dissipating requirement. It is still challenging to achieve satisfactory thermal conductivity enhancement with reasonable mechanical properties. Herein, we present a three-dimensional (3D), lightweight, and mechanically strong boron nitride (BN)-silicon carbide (SiC) skeleton with aligned thermal pathways via the combination of ice-templated assembly and hightemperature sintering. The sintering has introduced atomic-level coupling at the BN-SiC junction which contributes to efficient phonon transport via the newly formed borosilicate glass BC x N 3−x (0 ≤ x ≤ 3) and SiC x N 4−x (0 ≤ x ≤ 4) phases, leading to much lower interfacial thermal resistance. Thus, the obtained BN-SiC skeleton shows satisfactory thermal performance. The prepared 3D BN-SiC/polydimethylsiloxane (PDMS) composites exhibit a maximum through-plane thermal conductivity of 3.87 W•m −1 •K −1 at a filler loading of only 8.35 vol %. The thermal conductivity enhancement efficiency reaches 220% per 1 vol % filler when compared to pure PDMS matrix, superior to other reported BN skeleton-based composites. The feature of our strategy is to allow the oriented three-dimensional skeleton to be strongly bonded by a sintered ceramic phase instead of polymer-like adhesive, namely, to improve the intrinsic thermal conductivity of the skeleton to the greatest extent. This strategy can be applied to develop novel thermal management materials that are lightweight and mechanically tough that rapidly transfer heat. It represents a new avenue to addressing the heat challenges in traditional electronic products.